Know your waterproofs, water-resistant, and water repellents. It makes a massive difference to your trip if you’re warm and dry as opposed to soaking wet.
Not every raincoat is waterproof. Have a look at this guide to help you pick the level of protection you need for your trip.
I would stay away from ponchos, yes they are good in terms of being lightweight and easy to stuff in the bag but there’s nothing like wearing a poncho that makes you stand out as a tourist in a foreign city. You’ll put yourself at a high risk of pickpocketing. No one needs that.
These are the ones I use; you can see they range from lightweight to heavy and from casual to dressy.
You don’t need to have a range, invest in a good medium to light one, you can always layer underneath it to keep you warm.